Insights into the solution structure of the hydrated uranyl ion from neutron scattering and EXAFS experiments

Abstract

The solution structure of 1.0 M Uranyl Chloride has been determined by the EPSR modelling of a combination of neutron scattering and EXAFS data. The experimental data show an equilibrium in solution between [UO₂(H₂O)₅]²⁺ and [UO₂Cl(H₂O)₄]⁺ with a stability constant of 0.23 ± 0.03 mol⁻¹ dm⁻³. A much smaller fraction of the neutral [UO₂Cl₂(H₂O)₃] ion is also observed. The data also show, for the first time in solution, that the uranyl ion is a very poor hydrogen bond acceptor, but the coordinated waters show enhanced hydrogen bond ability compared to the bulk water.